Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEADgrafted

Changes:

Make expedited grace periods expedite normal RCU callbacks

Miscellaneous fixes:
 * Improve diagnostic output with character task states.
 * Mark accesses to inform KCSAN of concurrency design.
 * Move from kmalloc() to kmalloc_obj().
 * Documentation updates.
 * Improve handling of RCU deferred quiescent states.
 * Clean up unused function arguments and structure fields.
 * Reduce show_rcu_gp_kthreads() stack space.

Tasks RCU updates:
 * Clean up after SRCU re-implementation of Tasks Trace RCU.
 * Mark accesses to inform KCSAN of concurrency design.
 * Add ->lazy_timer status to diagnostic output.
 * Remove an unnecessary memory barrier.
 * Fix a data race, courtesy of KCSAN.
 * Documentation updates.
 * Convert cond_resched_tasks_rcu_qs() from macro to static inline
   function.

SRCU updates:
 * Add Rust helpers for SRCU.
 * Avoid losing queued work at cleanup_srcu_struct() time.

Torture-test updates:
 * Preparation work for immediate RCU priority deboosting.
 * Test RCU readers from real interrupt handlers (as opposed to softirq).
 * Simplify code through use of cpumask_next_wrap().
 * Improve diagnostic output with character task states.
 * Add rcutorture.nwriters parameter to allow lightweight stall testing,
   and rcutorture.stall_only to make doing so easier.
 * Test an RCU Tasks Trace grace period implying an RCU grace period.
 * Make RCU Tasks Trace torturing track reader batches.
 * Fix a data race, courtesy of KCSAN.
 * Plug a shuffle_tmp_mask memory leak on kthread spawn failure.

1 files changed, 172 insertions, 0 deletions

diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
new file mode 100644
index 000000000..8d46886d2
--- /dev/null
+++ b/security/lockdown/lockdown.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Lock down the kernel
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/security.h>
+#include <linux/export.h>
+#include <linux/lsm_hooks.h>
+#include <uapi/linux/lsm.h>
+
+static enum lockdown_reason kernel_locked_down;
+
+static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE,
+						 LOCKDOWN_INTEGRITY_MAX,
+						 LOCKDOWN_CONFIDENTIALITY_MAX};
+
+/*
+ * Put the kernel into lock-down mode.
+ */
+static int lock_kernel_down(const char *where, enum lockdown_reason level)
+{
+	if (kernel_locked_down >= level)
+		return -EPERM;
+
+	kernel_locked_down = level;
+	pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n",
+		  where);
+	return 0;
+}
+
+static int __init lockdown_param(char *level)
+{
+	if (!level)
+		return -EINVAL;
+
+	if (strcmp(level, "integrity") == 0)
+		lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX);
+	else if (strcmp(level, "confidentiality") == 0)
+		lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX);
+	else
+		return -EINVAL;
+
+	return 0;
+}
+
+early_param("lockdown", lockdown_param);
+
+/**
+ * lockdown_is_locked_down - Find out if the kernel is locked down
+ * @what: Tag to use in notice generated if lockdown is in effect
+ */
+static int lockdown_is_locked_down(enum lockdown_reason what)
+{
+	if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX,
+		 "Invalid lockdown reason"))
+		return -EPERM;
+
+	if (kernel_locked_down >= what) {
+		if (lockdown_reasons[what])
+			pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
+				  current->comm, lockdown_reasons[what]);
+		return -EPERM;
+	}
+
+	return 0;
+}
+
+static struct security_hook_list lockdown_hooks[] __ro_after_init = {
+	LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),
+};
+
+static const struct lsm_id lockdown_lsmid = {
+	.name = "lockdown",
+	.id = LSM_ID_LOCKDOWN,
+};
+
+static int __init lockdown_lsm_init(void)
+{
+#if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY)
+	lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX);
+#elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY)
+	lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX);
+#endif
+	security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks),
+			   &lockdown_lsmid);
+	return 0;
+}
+
+static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count,
+			     loff_t *ppos)
+{
+	char temp[80] = "";
+	int i, offset = 0;
+
+	for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
+		enum lockdown_reason level = lockdown_levels[i];
+
+		if (lockdown_reasons[level]) {
+			const char *label = lockdown_reasons[level];
+
+			if (kernel_locked_down == level)
+				offset += sprintf(temp+offset, "[%s] ", label);
+			else
+				offset += sprintf(temp+offset, "%s ", label);
+		}
+	}
+
+	/* Convert the last space to a newline if needed. */
+	if (offset > 0)
+		temp[offset-1] = '\n';
+
+	return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
+}
+
+static ssize_t lockdown_write(struct file *file, const char __user *buf,
+			      size_t n, loff_t *ppos)
+{
+	char *state;
+	int i, len, err = -EINVAL;
+
+	state = memdup_user_nul(buf, n);
+	if (IS_ERR(state))
+		return PTR_ERR(state);
+
+	len = strlen(state);
+	if (len && state[len-1] == '\n') {
+		state[len-1] = '\0';
+		len--;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
+		enum lockdown_reason level = lockdown_levels[i];
+		const char *label = lockdown_reasons[level];
+
+		if (label && !strcmp(state, label))
+			err = lock_kernel_down("securityfs", level);
+	}
+
+	kfree(state);
+	return err ? err : n;
+}
+
+static const struct file_operations lockdown_ops = {
+	.read  = lockdown_read,
+	.write = lockdown_write,
+};
+
+static int __init lockdown_secfs_init(void)
+{
+	struct dentry *dentry;
+
+	dentry = securityfs_create_file("lockdown", 0644, NULL, NULL,
+					&lockdown_ops);
+	return PTR_ERR_OR_ZERO(dentry);
+}
+
+#ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY
+DEFINE_EARLY_LSM(lockdown) = {
+#else
+DEFINE_LSM(lockdown) = {
+#endif
+	.id = &lockdown_lsmid,
+	.init = lockdown_lsm_init,
+	.initcall_core = lockdown_secfs_init,
+};